Method and apparatus for conditioning tobacco

ABSTRACT

The moisture content of a tobacco stream which contains a fixed quantity of tobacco per unit length is reduced during flow through a revolving drum which is heated by steam, oil or gaseous combustion products. At the same time, the tobacco stream exchanges heat with hot air which is conveyed through the drum counter to the direction of tobacco movement. The tobacco is thereupon cooled and its moisture content is measured to automatically adjust the temperature of heated air and the temperature of the drum when the measured moisture content deviates from a desired moisture content. The heating device for the drum is indirectly adjusted by a thermometer which measures the temperature of heated air. The regulating unit for the air heating device is directly connected with the unit which measures the moisture content of conditioned tobacco.

United States Patent Wochnowski METHOD AND APPARATUS FOR CONDITIONINGTOBACCO [75] Inventor: Waldemar Wochnowski, Hamburg,

Germany [73] Assignee: Hauni-Werke Korber & C0., KG,

Hamburg, Germany [22] Filed: Apr. 14, 1971 [21] Appl. No.: 134,004

[30] Foreign Application Priority Data Apr. 22, 1970 Germany P 20 19369.5

[52] US. Cl 131/140 R, 34/31, 34/48, 131/135 [51] Int. Cl A24 b 09/00,F26b 03/04 [58] Field of Search 131/140 R, 135, 136, 131/137; 34/46, 31,48

[56] References Cited UNITED STATES PATENTS 3,386,447 6/1968Wochnowski.... l3l/l40 R X 3,429,317 2/1969 Koch et a1 1 131/140 R2,827,058 3/1958 Bogaty 131/108 Primary Examiner-Robert W. MichellAssistant Examiner-.Iohn F. Pitrelli Att0rneyMichael S. Striker [57]ABSTRACT The moisture content of a tobacco stream which contains a fixedquantity of tobacco per unit length is re duced during flow through arevolving drum which is heated by steam, oil or gaseous combustionproducts. At the same time, the tobacco stream exchanges heat with hotair which is conveyed through the drum counter to the direction oftobacco movement, The tobacco is thereupon cooled and its moisturecontent is measured to automatically adjust the temperature of heatedair and the temperature of the drum when the measured moisture contentdeviates from a desired moisture content. The heating device for thedrum is indirectly adjusted by a thermometer which measures thetemperature of heated air. The regulating unit for the air heatingdevice is directly connected with the unit which measures the moisturecontent of conditioned tobacco.

20 Claims, 1 Drawing Figure METHOD AND APPARATUS FOR CONDITIONINGTOBACCO BACKGROUND OF THE INVENTION The present invention relates to amethod and apparatus for conditioning tobacco, and more particularly toa method and apparatus for changing the moisture content of a tobaccostream. Still more particularly, the invention relates to improvementsin a method and apparatus for reducing the moisture content of whole orcomminuted tobacco leaves.

It is already known to reduce the moisture content of tobacco byconveying a tobacco stream through a revolving drum which is heated bysteam and wherein the tobacco stream is heated by indirect exchange ofheat with the medium which heats the drum. The inertia of the heatingsystem for the drum is rather high; therefore, such drying apparatusnormally further comprise means for conveying through the rotating druma current of hot air which is thus caused to exchange heat with tobaccoand whose temperature can be changed much more rapidly than thetemperature of the drum. As a rule, the current of heated air is causedto flow through the drum in the same direction as the tobacco stream.Reference may be had to U.S. Pat. No. 3,372,488 to Koch et al., or toUS. Pat. No. 3,386,448 to Wochnowski. In a conditioning apparatus of thetype known as KLK and produced by I-Iauni-Werke, Kc'irber & Co. K.G., ofHamburg-Bergedorf, Western Germany, the moisture content of tobacco atthe inlet of the drum is measured by a detector, preferably of the typedisclosed in U.S,. Pat. No. 3,320,528 to Esenwein. Signals from thedetector are transmitted to a regulating unit which can rapidly changethe temperature of air as a function of the measured moisture contentand as a function of the quantity of tobacco which is being fed into thedrum per unit of time. A second detector measures the moisture contentof dried tobacco and adjusts the temperature of the drum when themeasured moisture content deviates from a desired moisture content. Theair which flows concurrent with the tobacco stream can rapidly changethe moisture content whereas the adjustment of heating device for thedrum compensates for longer-lasting deviations of moisture content fromthe desired value.

Problems arise when the current of heated air is to be conveyedcountercurrent to the movement of tobacco in the conditioning zone.Adjustments in air temperature as a function of the moisture content ofincoming tobacco would be of little avail because the flow of airAdditional problems'which arise in connection with 1 drying of tobaccoby air which is conveyed counter to the direction of tobacco flow areattributable to the fact that (due to the nature of treated material)the temperature of air cannot be increased at will and also that the aircannot be conveyed at a relatively high rate such as would enable theair to entrain the particles counter to the desired direction of tobaccomovement. Thus, the extent to which the heated air can influence themoisture content of tobacco in the conditioning zone is rather limited.On the other hand, drying of tobacco in a zone wherein the air flowscounter to the direction of tobacco movement presents severaladvantages, such as elimination of a detector and continuous contactingof tobacco at the discharge end of the conditioning zone with freshlyadmitted hot air.

SUMMARY OF THE INVENTION An object of the invention is to provide animproved method of reducing the moisture content of tobacco in aconditioning zone wherein a stream of hot gaseous fluid is caused toflow counter to the direction of tobacco movement. 7

Another object of the invention is to provide a method of reducing themoisture content of a tobacco stream to a desired value withoutnecessitating a measurement of the moisture content upstream of theconditioning zone.

A further object of the invention is to provide an improved method ofreducing the moisture content of tobacco in a conditioning zone whereinthe treated material is heated indirectly by a first medium which heatsthe conveyor for tobacco and directly by a gaseous fluid which flowscounter to the direction of tobacco movement.

An additional object of the invention is to provide a novel and improvedtobacco drying apparatus which is capable of automatically adjusting itsmoisture expelling action when the moisture content of treated materialdeviates from a desired moisture content.

The method of the present invention comprises the.

steps of conveying a stream of moist tobacco in a predetermineddirection through an elongated conditioning zone, subjecting tobacco inthe conditioning zone to the indirect heating action of a first fluid(preferably by heating with steam or the like a conveyor whichtransports tobacco through the conditioning zone), subjecting tobacco inthe conditioning zone to the direct heating action of a second fluid(preferably air) by conveying such fluid through the conditioning zonecounter to the direction of tobacco transport whereby the moisturecontent of tobacco in such zone is reduced as a consequence of thedirect and indirect heating actions, measuring the moisture content oftobacco downstream of the conditioning zone, comparing the result of themeasurement with a predetermined (desired) moisture content, andadjusting the direct and indirect heating actions in response todeviations of the result of measurement from the predetermined value.The indirect heating action is preferably at least substantially uniformthroughout the entire conditioning zone; this can be achieved byemploying a tubular conveyor which surrounds the conditioning zone andis heated by coils for circulation of steam, oil or gaseous combustionproducts.

The adjusting step preferably comprises changing the temperature of thesecond fluid and changing the pres sure or the rate of circulation ofthe first fluid. In accordance with one presently preferred embodimentof the method, the adjustingstep comprises measuring the temperature ofthe second fluid, at least while such temperature changes as a functionof deviations of the result of measurement of moisture content from thepredetermined value, and changing the indirect heating thermometer whichdetermines the temperature of the aforementioned conveyor), comparingthe thus detected intensity of indirect heating action with apredetermined value, and changing the indirect heating action inresponse to deviations of the detected intensity from a desiredintensity. Thus, the indirect heating action can be changed independency on changes in temperature of the second fluid as well as independency on deviations of the intensity of indirect heating actionfrom a desired intensity.

In accordance with a more specific feature of the invention, thetemperature of the second fluid can be changed in response to deviationsof the detected intensity of indirect heating action from the desiredintensity to normally maintain the second fluid at an averagetemperature which can be rapidly raised to compensate for suddenincreases in moisture content or rapidly reduced to compensate forabrupt reductions of moisture content.

The indirect heating action can be changed or regulated in dependency onthe changes in temperature of the second fluid and in dependency on atleast one other factor, such as the pressure of the first fluid which isused to heat the aforementioned conveyor or the speed at which thetemperature of the second fluid changes.

The method preferably further comprises the step of cooling the tobaccosubsequent to heating and prior to measurement of its moisture content.

In accordance with still another feature of the improved method, moisttobacco is supplied to the conditioning zone at a rate which is at leastsubstantially constant. This can be achieved by employing a weighingdevice which weighs successive unit lengths of moist tobacco andcontrols a drive which determines the rate at which moist tobacco isbeing withdrawn from a magazine or the like.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved conditioning apparatus itself, however, both as to itsconstruction and its mode of operation, together with additionalfeatures and advantages thereof, will be best understood upon perusal ofthe following detailed description of certain specific embodiments withreference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is a partlydiagrammatic and partly elevational view of a conditioning apparatuswhich embodies the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus which isillustrated in the drawing comprises an adjustable tobacco feeding unit1 which can supply a stream S of moist tobacco wherein each unit lengthcontains the same quantity of material. The apparatus further comprisesa drying or conditioning unit 2 wherein the stream S is subjected to adrying or moisture-reducing treatment, a cooling unit 3 wherein thetreated (and thus heated) tobacco is cooled, and a measuring unit 4which determines the moisture content of successive increments of thetreated and cooled stream.

The adjustable feeding unit 1 comprises a magazine or hopper 7 whichcontains a supply of moist tobacco leaves and/or shreds and one sidewall of which is formed by the upwardly moving stretch of an endlesstobacco withdrawing conveyor here shown as a feed apron 6 which showerstobacco onto the upper stretch of an endless conveyor 8a forming part ofa weighing device 8. The weighing device 8 produces signals indicatingthe weight of successive increments of the tobacco stream which isformed on the upper stretch of the conveyor 80, and such signals areutilized to regulate the speed of the apron 7 by means of a d-c motor13. The operative connection between the weighing device 8 and the motor13 comprises a transducer 9 which converts mechanical or pneumaticsignals furnished by the weighing device 8 into electrical signals whichare transmitted to a conventional signal comparing junction 10. At thisjunction, the signal from the transducer 9 is compared with a referencesignal furnished by an adjustable potentiometer 14, and thejunction 10produces a positive or a negative signal when the intensity of thesignal furnished by the transducer 9 is less than or exceeds theintensity of signal from the potentiometer 14. The latter furnishes asignal which represents the desired quantity of tobacco per unit lengthof the stream S. The output signal from the junction 10 is amplified,first by a preamplifier l1 and thereupon by an operational amplifier 12,and is transmitted to the motor 13 which drives the lower pulley for theapron 6 at a greater or lesser speed, depending on the sign of thesignal from the junction 10.

The drying or conditioning unit 2 comprises a hollow rotary tubularconveyor here shown as a drum 16 whose interior defines an elongatedconditioning zone and which is mounted for rotation on guide rollers 17and 18. An electric motor 19 drives a pinion 19a which meshes with aring gear 19b of the drum 16 so that the latter is rotated when thecircuit of the motor 19 is completed. The motor 19 is assumed to rotatethe drum 16 at a constant speed. The axis of the drum 16 is slightlyinclined in a downward direction, as considered in the direction oftravel of the tobacco stream S, so as to insure that the streamautomatically advances from the left-hand end or intake end toward andbeyond the right-hand end or discharge end of the drum 16. The endlessconveyor 8a of the weighing device 8 discharges tobacco into an inclinedchute 20 which feeds such tobacco into the intake end of the'drum 16.This intake end is otherwise sealed by a hood 24a which is connectedwith an exhaust fan 24 serving to collect vapors and spent gaseousheating medium and to withdraw such fluids at the upstream end of theconditioning zone in the drum 16.

The tobacco which passes through the conditioning zone in the drum 16 istreated (heated) directly by a hot gaseous fluid (preferably air) whichis admitted at the discharge end of the drum. The current of heated airflows countercurrent to the tobacco stream S and contacts all or nearlyall particles of tobacco because the particles in the conditioning zoneare subjected to an intensive agitating action by heating coils 26 whichare mounted in and orbit about the axis of the drum 16 when the circuitof the motor 19 is completed. The heating coils 26 act not unlike bladesor paddles by repeatedly lifting tobacco from the bottom part of theconditioning zone and by showering the lifted particles in the upperpart of such zone. The source of hot gaseous fluid is a blower 22 whoseintake end is connected with a conduit 22a containing at its inlet anelectric resistance heater 23. The outlet of the blower 22 is connectedwith the discharge end of the drum 16 by means of a supply pipe 21.

A second hot gaseous fluid (preferably steam) is stored in compressedcondition in a tank 27 or a similar source and is fed to and circulatedthrough the heating coils 26 by means of a supply pipe 28 containing anadjustable valve 64 and discharging steam into a distributor 29. It isclear that the source 27 of steam can be replaced with a source ofanother fluid, such as hot gaseous combustion products of an internalcombustion engine or air or oil which is heated by one or more burnersor the like. The fluid (hereinafter called steam) which circulatesthrough the coils 26 and is widthdrawn by way of the distributor 29 iscaused to indirectly exchange heat with tobacco in the conditioning zonewithin the rotating drum 16. On the other hand, the hot gas'(hereinaftercalled air) which flows countercurrent to the tobacco stream S and isfurnished by the supply pipe 21 is in direct heat exchanging contactwith tobacco.

The apparatus further comprises a regulating unit 31 which serves toregulate the temperature of air admitted' by way of the supply pipe 21,and a regulating unit 51 which serves to regulate the intensity ofheating action of steam furnished by the distributor 29, i.e., thetemperature of the drum 16.

The regulating unit 31 comprises a potentiometer which constitutes asource of reference signals representing the desired moisture content oftreated and cooled tobacco, a conventional junction 32 which receivessignals from a detector (thermometer) 34 mounted in the supply pipe 21and serving to produce signals which are indicative of the temperatureof air flowing into the drum 16, and from another detector (thermometer)55 which measures the temperature of the drum 16 (Le, the intensity ofthe indirect heating action of steam) and transmits signals which areindicative of such temperature. The detectors 34, 55 respectivelytransmit signals to the corresponding inputs of the junction 32 by wayof amplifiers 36, 60. The junction 32 transmits signals to a secondjunction 33 of the regulating unit 31; the junction 33 further receivessignals from the potentiometer 30 (by way of a third junction 35) andtransmits signals, by way of conductor means 48, to two signalgenerating or energizing devices 37a, 37b of the regulating unit 31. Thedevices 37a, 37b respectively control relays 38a, 38b for a servomotor41 which can pivot an adjustable flap or valve 42 in the aforementionedconduit 22a to thus bring about rapid changes in the temperature of airwhich enters the supply pipe 21. The flap 42 controls the admission ofrelatively cool atmospheric air into a mixing zone 43 in the interior ofthe conduit 22a. Such mixing zone receives a constant stream of airwhich enters the inlet of the conduit 22a and is heated by the electricheater 23. The parts. 21, 22, 22a, 23 constitute an adjustable heatingdevice for air and the parts 41, 42 constitute an adjusting device 39for the heating device and hence a means for determining and changingthe temperature of air which enters the supply pipe 21. The servomotor41 is preferably a d-c motor which can rotate its output shaft in afirst direction (in response to energization of one of the relays 38a,38b) to thereby change the position of the flap 42 for the purpose ofadmitting more cool air into the mixing zone 43 and in a seconddirection (in response to energization of the other relay) to therebymove the valve 42 in a direction to reduce the inflow of cool air intothe mixing zone 43.

The signal generating devices 37a, 37b respectively comprise voltagesources 44a, 44b for periodic transmission of sawtooth-shaped voltagepulses, pairs of resistors 46a, 46b, junctions a, 45b and operationalamplifiers 47a, 47b. Depending on the polarity of voltage signalstransmitted by the conductor means 48, the device 37a or 37b transmitsto the respective relay 38a or 38b a signal which results inenergization of the respective relay and in appropriate adjustment ofthe flap 42 by the servomotor 41. The duration of signals furnished bythe devices 37a, 37b depends on the intensity of signals from thejunction 33. The servomotor 41 remains in operation for a longer orshorter period of time, depending on the extent to which the position ofthe flap 42 must be adjusted in order to insure that the temperature ofhot air in the supply pipe 21 will correspond to a desired temperature.The length of the aforementioned periods depends on the intensity ofsignal which is trnasmitted by the conductor means 48. The intensity ofsawtooth-shaped signal furnished-by the source 44a or 44b risesgradually and the energization of relay 38a or 3812 is terminated whenthe intensity of the signal from 44a or 44b matches the intensity ofsignal from the junction 33. The signal from the junction 33 to thejunction 45a or 45b is compared with the signal from the source 44a or44b, and the signal which represents the difference between theintensities of signals furnished to the inputs of the junction 45a or45b is thereupon amplified at 47a or 47b prior to transmission to therelay 38a or 38b. The intensity of signals furnished by the amplifiers47a, 47b to the respective relays 38a, 38b is constant and thetransmission of such signals is terminated when the signal from junction33 to junction 45a or 45b is matched by the signal from the source 44aor 44b. Thus, the servomotor 41 is automatically arrested when thejunction 33 ceases to furnish a signal to the associated resistor 46a or46b, namely, when the junction 32 furnishes to the corresponding inputof the junction 33 a signal which matches the signal from the junction35.

The regulating unit 51 for the temperature of the drum 16 comprises ajunction 52 which is connected with the aforementioned detector 55 byway of the amplifier and with the detector 34 by way of the amplifier36. The'junction 52 transmits signals to a second junction 53 which isfurther connected with a source of reference signals here shown as anadjustable potentiometer 54. The output of the junction 53 is connectedwith a junction 56 which is further connected with a signal-generatingpressure measuring gauge 57 in the supply pipe 28 by means of anamplifier 58. The output of the junction 56 (which is analogous to thejunction 33 of the regulating unit 31) is connected by conductor means71 with two signal generating or energizing devices 59a, 59b. The gauge57 transmits signals which are indicative of the pressure of steam inthe supply pipe 28. The signal generating devices 59a, 59b respectivelyserve to energize two relays 61a, 61b for a d-c servomotor 63(corresponding to the motor 41 of the regulating unit 31) and serving toadjust the aforementioned valve 64 in the supply pipe 28 which admitssteam from the source 27 to the distributor 29. The parts 26, 27, 28, 29constitute an adjustable heating device for the drum l6 and the motor 63and the valve 64 constitute an adjusting device 62 which controls theheating device for the drum 16 by determining the rate of admisssion ofsteam into the coils 26 in dependency on the (positive or negative) signof signals which are transmitted by the conductor means 71. As explainedin connection with the relays 38a, 38b and servomotor 41, the relays61a, 61b in the regulating unit 51 respectively serve to cause rotationof the motor 63 in opposite directions to thereby adjust the valve 64 ina direction to either increase or reduce the flow of steam into thedistributor 29.

The signal generating devices 59a, 59b respectively comprise sources66a, 66b of sawtooth-shaped voltage pulses, junctions 68a, 68b, pairs ofresistors 67a, 67b and operational amplifiers 69a, 69b. The sources 66a,66b transmit sawtooth-shaped pulses depending on the sign of the voltagesignal which is transmitted by the conductor means 71. The relay 61a or61b is energized when the intensity of signal furnished to the junction68a or 68b by the conductor means 71 exceeds the intensity of thegradually rising signal from the soruce 660 or 66b. The sources 44a, 44band 66a, 66b transmit signals periodically. The servomotor 63 adjuststhe valve 64 as long as one of the relays 61a, 61b remains energized,namely, as long as the intensity of signal from the junction 56 to thejunction 68a or 68b exceeds the intensity of signal from the source 660or 66b.

The cooling unit 3 comprises an elongated pneumatic conveyor 77 whichreceives tobacco by way of a chute 76 at the discharge end of the drum16. The discharge end of the conveyor 77 is. connected with a suctionfan 78 which withdraws the gaseous carrier for tobacco. The tobacco isseparated from air in a separator 79a and is withdrawn from thepenumatic conveyor 77 by way of an air lock 79. The latter dischargesthe treated and cooled tobacco into a vibrating trough 82 which containsa moisture detector 81, preferably of the type disclosed in US. Pat. No.3,320,528 to Esenwein. The detector 81 forms part of the measuring unit4 which is preferably of the type known as HWK and is furnished byHauni-Werke, Kr'a'rber & Co. KG, of Hamburg-Bergedorf, Western Germany.Reference may be had to US. Pat. No. 3,372,488 to Koch et al. Thedetector 81 is a capacitor having two electrodes which are installed inthe trough 82 and are connected with an oscillator circuit 83. Thelatter is loosely coupled to a high frequency generator 84. Theamplitudes of oscillations of the circuit 83 are indicative of themoisture content of tobacco issuing from the air lock 79. The signalsfrom the oscillator circuit 83 are amplified by an amplifier 86 and aretransmitted to the junction 35 in the regulating unit 31.

An endless conveyor 87 is provided to convey tobacco from the trough 82to a further processing station.

A conductor 88 connects the regulating unit 31 with the regulating unit51 and contains a differential circuit 89 and a threshold circuit 91.The latter is connected with the junction 56 by a conductor 92. Thecircuit 89 transmits to the junction 56 a signal which is indicative ofthe changes in intensity of signal transmitted from the detector 34 bythe conductor 89. The circuit 91 permits such signal to reach thejunction 56 only if the intensity of the signal exceeds a predeterminedthreshold value.

THE OPERATION The motor 13 is assumed to drive the apron 6 so that thelatter withdraws from the magazine 7 a continuous stream S of moisttobacco which is showered onto the endless conveyor 8a of the weighingdevice 8. The moisture content of tobacco in the magazine 7 exceeds thedesired moisture content as indicated by the signal from thepotentiometer 30. The device 8 weighs the thus withdrawn moist tobaccoand transmits signals to the transducer 9. The tobacco stream S entersthe rotating heated drum 16 by way of the chute 20 and is agitated bythe coils 26. The transducer 9 transmits an electric signal which isindicative of the weight of tobacco on the conveyor and the junction 10compares such signal with the reference signal furnished by thepotentiometer 14. If the weight of tobacco on the conveyor 8a exceeds oris less than the desired weight (reference signal from the potentiometer14), the amplifiers 11, 12 receive a signal and cause the motor 13 torotate at a different speed to thus cause the apron to withdraw agreater or lesser quantity of tobacco from the magazine 7. Thus, thedrum 16 is assumed to receive equal quantities of tobacco per unit oftime so that the conditioning unit 2 must perform the sole function ofchanging the moisture content of tobacco during travel through theconditioning zone.

That portion of the stream S which passes through the drum 16 isindirectly heated by steam which circulates in the coils 26. Such steamheats not only the coils 26 but also the cylindrical wall of the drum16. In addition, tobacco in the conditioning zone is heated by air whichis admitted by the supply pipe 21 and flows counter to the direction oftobacoo transport from the chute 20 toward the chute 76. The thustreated portions of the stream S are then admitted into the pneumaticconveyor 77 and are cooled during transport toward the air lock 79. Thetransport of tobacco in the conveyor 77 takes place in response togeneration of an air stream which is produced by the suction fan 78.

The tobacco which is separated from air in the device 790 descends intothe vibrating trough 82 and its moisture content is determined by themeasuring unit 4, namely, by the capacitor which includes the electrodes81 in the trough 82. The tobacco is then transferred onto the endlessconveyor 87.

The measuring unit 4 produces an electric signal which is amplified at86 and is transmitted to the corresponding input of the junction 35 inthe regulating unit 31. The other input of the junction 35 receives areference signal from the adjustable potentiometer 30; such referencesignal is indicative of the desired moisture content of tobacco whichleaves the conditioning apparatus.

If the intensity of signal furnished by the amplifier 86 does not matchthe intensity of reference signal from the potentiometer 30, thejunction 35 transmits an appropriate signal to the junction 33. If themeasured moisture content of tobacco in the trough 82 is too high, theregulating unit 31 causes the adjusting device 39 to reduce the inflowof cool air by way of the flap 42 so that the temperature of air in thesupply conduit 21 rises and the tobacco in the conditioning zone issubjected to a more intensive heating action. The transmission of signalfrom the junction 33 to the signal generating or energizing device 37aor 37b is terminated when the intensity of signal from the junction 35is matched by the intensity of signal from the detector 34, Le, when thedetector 34 indicates that the temperature of air in the supply conduithas been increased or reduced to the extent which is necessary toconform the moisture content of tobacco in the trough 82 to thepredetermined moisture content (reference signal from the potentiometer30). The junction 33 receives from the junction 32 a signal which isindicative of the temperature of air in the supply pipe 21 as well as ofthe temperature of the drum 16 so that the adjustment of servomotor 41for the flap 42 is terminated when the signal from the junction 35 tothe junction 33 is matched by the signal from junction 32 which isindicative of the temperature of hot air as well as of temperature ofthe drum 16. As mentioned before, the temperature of the drum 16 ismeasured by the detector 55. The energization of relay 38a or 38b in theregulating unit 31 in response to a positive or negative signal from thejunction 33 (by way of the conductor means 48) takes place in theaforedescribed manner. The adjustment is completed within a perioddetermined by the source 44a or 44b which transmits signals periodicallyand for certain intervals of time. The length of the interval duringwhich the relay 38a or 38b remains energized in order to cause theservomotor 41 to move the flap 42 toward a closed or toward a fully openposition depends on the intensity of signal from the junction 33 to thedevice 37a or 37b. If the moisture content of tobacco in the trough 82is excessive, the signal from the junction 33 causes one of the relays38a, 38b to complete the circuit of the servomotor 41 in such a way thatthe flap.42 is moved toward the closed position to thus reduce thequantity of cool air which enters the mixing zone 43 downstream of theheater 23. The fully or nearly fully closed position of the flap 42 isindicated by a phantom line; in such position of the flap 42, theregulating unit 31 insures that the temperature of air in the supplypipe 21 is rather high to thus effect the expulsion of greaterquantities of moisture from tobacco which is conveyed through theconditioning zone. The regulating unit 31 reacts very rapidly so thatthe deviation of moisture content of tobacco leaving the conditioningapparatus from a desired moisture content is of short duration.

The signal which is furnished by the detector 34 is further transmittedto the junction 52 by way of the conductor 88. The junction 52 computessuch signal with the signal from the detector 55 and transmits to thejunction 53 a signal which is indicative of the sum of signals from thedetectors 34 and 55. If such signal does not match the signal from theadjustable potentiometer 54, the junction 53 transmits an appropriatesignal to the junction 56. The latter further receives a signal from thegauge 57 which measures the pressure of steam in the supply pipe 28.Depending on the positive or negative sign of the signal from thejunction 56, the signal generating device 59a or 59b energizes the relay61a or 61b to thus enable the servomotor 63 to increase or to reduce theadmission of steam from the source 27 into the coils 26 and to therebyraise or reduce the temperature of the drum 16. Thus, the adjustingdevice 62 determines the pressure of steam which is circulated inthecoils 26. The arrangement is such that, when the conductor 88transmits from the detector 34 a signal which indicates that thetemperature of air in the supply pipe 21 is on the increase, theregulating unit 51 raises the temperature of the drum 16 to thus insurea rapid reaction of the conditioning apparatus in the event that themoisture content of tobacco in the trough 82 is too high. Analogously,when the signal from the detector 34 indicates that the temperature ofair in the supply pipe 21 is on the decrease, the regulating unit 51reduces the pressure of steam in the coils 26 to thus reduce thetemperature of the drum 16. The servomotor 63 can be designed to adjustthe valve 64 in stepwise fashion or continuously during the interval ofenergization of the relay 610 or 61b.

The inertia of the heating device which includes the coils 26 is greaterthan the inertia of the heating device which includes the blower 22,i.e., an adjustment in the position of the flap 42 by the servomotor 41is followed by a change in temperature of air issuing from the supplypipe 21 practically without any delay. The reaction of the heatingdevice 26-29 is slower. Therefore, once the regulating unit 51 hasstarted the adjustment of the valve 64 in a direction to either increaseor reduce the temperature of the drum 16, the flap 42 is preferablyreturned to the illustrated intermediate or neutral position so that itcan again cause a practically instantaneous reaction of the air heatingdevice 21,22, 22a 23 if the moisture content of tobacco in the trough 82deviates from the desired moisture content. In the neutral position ofthe flap 42, the regulating unit 31 is in a condition to rapidly shutoff the inflow of cool air into the mixing zone 43 or to increase theinflow of cool air to a maximum value.

The return movement of flap 42 to the illustrated neutral position iseffected by a signal from the detector 55 to the junction 32. When thetemperature of the drum 16 reaches the desired value, i.e., when theheating action of the drum l6'and coils 26 can insure that the moisturecontent of tobacco leaving the pneumatic conveyor 77 is within thedesired range, the junction 33 transmits a signal which causes thedevice 370 or 37b of the regulating unit 31 to energize the relay 38a or38b so as to return the flap 42 to the illustrated neutral position. Thedetector 34 then furnishes a different signal (because the temperatureof air in the supply pipe 21 either rises or decreases, depending uponwhether the flap 42 has been moved to the neutral position from an openposition or from a closed position) which is transmitted to the junction52 and thence to the junction 53. The junction 53 furnishes a signalwhich is a reference signal for the desired'position of the valve 64(junction 56).

The circuits 89 and 91 are provided for the purpose of enabling theapparatus to rapidly react to sudden and substantial changes in moisturecontent of tobacco which is caused to advance in the trough 82. Thesignal from the detector 34 is then transmitted to the junction 56 (byway of the conductors 88, 92 and circuits 89, 91) so that the signalfrom the junction 56 to the signal generating device 59a or 59b of theregulating unit 51 is intensified with the attendant rapid change in theposition of valve 64. The signal from the threshold circuit 91disappears as soon as its intensity decreases below a predeterminedvalue.

As mentioned before, the steam is but one of heating fluids which can becirculated in the coils 26 to heat the drum 16 and to indirectly heattobacco in the conditioning zone. The coils 26 can be used forcirculation of gaseous combustion products, oil or another suitablegaseous or liquid fluid.

The heating device 21, 22, 22a, 23 can react, almost without any delay,to signals from the junction 33 of the regulating unit 31 to rapidlychange the heating action of air in response to actuation of theadjusting means 39. The heating device 26-29 for the drum 16 is slower(i.e., its inertia is higher); therefore, the rapid change in heatingaction of air which flows countercurrent to the tobacco stream in theconditioning zone is accompanied by a longer-lasting change in theheating action of the drum. Once the heating action of the drum 16 hasbeen altered sufficiently to insure that tobacco issuing from theconditioning zone will haVe a desired moisture content while the valve42 dwells in the illustrated intermediate (half open) position, thesignal from the junction 32 to junction 33 causes the regulating unit 31to actuate its adjusting means 39 in order to reset the flap 42 to theposition which is shown by the solid line.

The circuit 89 insures that the valve 64 is adjusted to a greater extentin response to abrupt changes in the temperature of air flowing throughthe supply pipe 21, i.e., in response to a substantial adjustment of theflap 42 when the measuring unit 4 indicates that the moisture content oftobacco leaving the drum 16 has suddenly changed and deviatesconsiderably from the desired moisture content as indicated by thesignal from the potentiometer 30. This can take place when the magazine7 receives a fresh batch of tobacco with a moisture content which ismuch higher than or well below the moisture content of the precedingbatch. When the fluctuations of the measured moisture content are lesspronounced, signals which reach the junction 56 from the junction 53 andgauge 57 (without a signal from the circuit 89) suffice to effectappropriate adjustments of the heating device 26-29.

It will be noted that the measuring unit 4 is directly connected withthe regulating unit 31 and that such measuring unit is indirectlyconnected with the regulating unit 51 by way of the detector 34 of theunit 31. Thus, the heating device 21, 22, 22a, 23 responds almostimmediately to all detected changes in moisutre content of the treatedand cooled tobacco stream whereas the heating device 26-29 respondsindirectly by changing the heating action upon the drum 16 in responseto changes in the temperature of air flowing through the supply pipe 21.Such response is intensified by differentiating the signal from thedetector 34 to the junction 56 for the signal generating devices 59a,59b of the regulating unit 51.

The signal from the detector 55 to the junction 32 insures that theadjustment of the flap 42 (and hence the temperature of air in thesupply pipe 21) is influenced by the temperature of the drum 16. Suchadjustment is terminated when the drum 16, together with air whosetemperature corresponds to that at the intermediate setting of the flap42, can insure that the moisture content of treated tobacco is withinthe desired range. In such position of the flap 42, the adjusting device39 is ready to bring about substantial changes in the temperature of airin the supply pipe 21 (by moving the flap 42 to the fully open or to thefully closed position). Cooling of tobacco subsequent to conditioninginsures that signals furnished by the measuring unit 4 accuratelyreflect the moisture content of conditioned tobacco without suchdistortions which would occur if the unit 4 were to measure the moisturecontent of tobacco at different temperatures. The weighing device 8contributes to a more uniform conditioning action by insuring that eachunit length of the stream S contains the same quantity of tobacco. Thus,as a rule, any fluctuations in the moisture content of treated tobaccoare attributable to a single factor, namely, to fluctuations in moisturecontent of tobacco in the magazine 7.

An important advantage of the improved conditioning apparatus is that itinsures rapid changes in moisture content even though the air is causedto flow countercurrent to movement of tobacco in the conditioning zone.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of my contribution to the art and, therefore, suchadaptations should and are intended to be comprehended within themeaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended 1. A method of conditioning tobacco,comprising the steps of conveying a stream of moist tobacco on aconveyor in a predetermined direction through an elongated conditioningzone; subjecting tobacco in said conditioning zone to indirect heatingaction by heating the conveyor; subjecting tobacco in said conditioningzone to the direct heating action ofa fluid by conveying said fluidthrough said conditioning zone counter to said direction with attendantreduction of the moisture content of tobacco as a consequence of saiddirect and indirect heating actions; measuring the moisture content oftobacco downstream of said conditioning zone; comparing the result ofsuch measurement with a predetermined value; automatically adjustingsaid direct and indirect heating actions in response to deviations ofsaid result from said predetermined value; and adjusting one of saidheating actions in dependency upon the other of said heating actions.

2. A method as defined in claim 1, wherein said indirect heating actionis substantially uniform throughout said conditioning zone.

3. A method as defined in claim 1, wherein said first mentionedadjusting step comprises changing the temperature of said fluid.

4. A method of conditioning tobacco, comprising the steps of conveying astream of moist tobacco on a conveyor in a predetermined directionthrough an elongated conditioning zone; subjecting tobacco in saidconditioning zone to the indirect heating action of a first fluid byutilizing the first fluid to heat the conveyor; subjecting tobacco insaid conditioning zone to the direct heating action ofa second fluid byconveying the second fluid through said conditioning zone counter tosaid direction with attendant reduction of the moisture content oftobacco as a consequence of said direct and indirect heating actions;measuring the moisture'content of tobacco downstream of saidconditioning zone; comparing the result of such measurement with apredetermined value; and automatically adjusting said direct andindirect heating actions in response to deviations of said result fromsaid predetermined value, said adjusting step comprising changing thetemperature of said second fluid, measuring the temperature of saidsecond fluid, and changing said indirect heating action in response tochanges in the temperature of said second fluid.

5. A method of conditioning tobacco, comprising the steps of conveying astream of moist tobacco on a conveyor in a predetermined directionthrough an elongated conditioning zone; subjecting tobacco in saidconditioning zone to the indirect heating action of a first fluid byutilizing the first fluid to heat the conveyor; subjecting tobacco insaid conditioning zone to the direct heating action of a second fluid byconveying the second fluid through said conditioning zone counter tosaid direction with attendant reduction of themoisture content oftobacco as a consequence of said direct and indirect heating actions;measuring the moisture content of tobacco downstream of saidconditioning zone; comparing the result of such measurement with apredetermined value; automatically adjusting said direct and indirectheating actions in response to deviations of said result from saidpredetermined value, including changing the temperature of said secondfluid; measuring the intensity of said indirect heating action;producing first and second signals respectively indicating thetemperature of said second fluid and the intensity of said indirectheating action; and changing the intensity of said indirect heatingaction in accordance with said signals.

6. A method as defined in claim 5, wherein said adjusting step furthercomprises changing the temperature of said second fluid in accordancewith said second signal.

7. A method as defined in claim 4, wherein said indirect heating actionis changed in dependency on changes in temperature of said second fluidas a function of time.

8. A method as defined in claim 1, further comprising the step ofcooling the tobacco which issues from said conditioning zone prior tosaid measuring step.

9. A method as defined in claim 1, further comprising the step ofsupplying to said conditioning zone moist tobacco at an at leastsubstantially constant rate.

10. Apparatus for conditioning tobacco, comprising a conveyor definingan elongated conditioning zone; feeding means for delivering to saidconveyor a stream of moist tobacco whereby such stream advances in apredetermined direction through and beyond said conditioning zone; firstadjustable heating means for heating said conveyor to thereby subjecttobacco in said zone to a first heating and moisture-expelling action;second adjustable heating means for conveying through said conditioningzone a hot fluid counter to said direction to thus subject tobacco insaid zone to a second heating and moisture-expelling action; measuringmeans for determining the moisture content of tobacco after the tobaccoissues from said conditioning zone; and regulating means connected withsaid measuring means and operative to adjust said first and secondheating means in response to deviations of that moisture content whichis detected by said measuring means from a predetermined value and foradjusting the heating action of one of said heating means in dependencyupon the heating action of the other of said heating means.

11. Apparatus as defined in claim 10, wherein said conveyor comprises atubular member which surrounds said conditioning zone and said firstheating means is arranged to heat said tubular member, said tubularmember having an intake end for admission of tobacco and a discharge endfor evacuation of tobacco and for admission of said hot fluid.

12. Apparatus as defined in claim 10, wherein said regulating meanscomprises discrete first and second regulating units for said first andsecond heating means and said second regulating unit comprises adjustingmeans for changing the'temperature of said fluid as a function of saiddeviations.

13. Apparatus for conditioning tobacco, comprising a conveyor definingan elongated conditioning zone;

feeding means for delivering to said conveyor a stream of moist tobaccowhereby said stream advances in a predetermined direction through andbeyond said conditioning zone; first adjustable heating means forheating said conveyor to thereby subject tobacco in said zone to a firstheating and moisture-expelling action; second adjustable heating meansfor conveying through said conditioning zone a hot fluid counter to saiddirection to thus subject tobacco in said zone to a second heating andmoisture-expelling action; measuring means for determining the moisturecontent of tobacco after the tobacco issues from said conditioning zone;

and regulating means connected with said measuring means and operativeto adjust said first and second heating means in response to deviationsof that moisture content which is detected by said measuring means froma predetermined value, said regulating means comprising discrete firstand second regulating units for said first and second heating means,said measuring means being connected with said second regulating unit toeffect changes in the temperature of said fluid in response to saiddeviations and said second regulating unit comprising detector means forproducing signals indicating the temperature of said fluid, said firstregulating unit being responsive to said signals to adjust said firstheating means as a function of changes in the temperature of said fluid.

14. Apparatus for conditioning tobacco, comprising a conveyor defining aelongated conditioning zone; feeding means for delivering to saidconveyor a stream of moist tobacco whereby said stream advances in apredetermined direction through and beyond said conditioning zone; firstadjustable heating means for heating said conveyor to thereby subjecttobacco in said conditioning zone to a first heating andmoistureexpelling action; second adjustable heating means for conveyingthrough said conditioning zone a hot fluid counter to said direction tothus subject tobacco in said conditioning zone to a second heating andmoistureexpelling action; measuring means for determining the moisturecontent of tobacco after the tobacco issues from saidconditioning zone;and regulating means connected with said measuring means and operativeto adjust said first and second heating means in response to deviationsof that moisture content which is detected by said measuring means froma predetermined value, said regulating means comprising discrete firstand second regulating units for said first and second heating means andsaid first and second regulating units respectively comprising first andsecond detector means for producing first and second signalsrespectively indicating the temperature of said conveyor and thetemperature of said fluid, said first regulating unit further comprisingadjusting means for adjusting said first heating means to thereby changethe temperature of said conveyor in response to said signals, saidsecond regulating unit including adjusting means for changing thetemperature of said fluid in response to said deviations.

15. Apparatus for conditioning tobacco, comprising a conveyor definingan elongated conditioning zone; feeding means for delivering tosaidconveyor a stream of moist tobacco whereby said stream advances in apredetermined direction through and beyond said conditioning zone; firstadjustable heating means for heating said conveyor to thereby subjecttobacco in said conditioning zone to a first heating andmoistureexpelling action; second adjustable heating means for conveyingthrough said conditioning zone a hot fluid counter to said direction tothus subject tobacco in said conditioning zone to a second heating andmoistureexpelling action; measuring means for determining the moisturecontent of tobacco after the tobacco issues from said conditioning zone;and regulating means connected with said measuring means and operativeto adjust said first and second heating means in response to deviationsof that moisture content which is detected by said measuring means froma predetermined value, said regulating means comprising discrete firstand second regulating units for said first and second heating means andsaid first and second regulating units respectively comprising first andsecond detectors for producing signals respectively indicating thetemperature of said conveyor and the temperature of said fluid, saidsecond regulating unit further comprising adjusting means for changingthe temperature of said fluid as a function of signals from said firstdetector and in response to said deviations.

16. Apparatus as defined in claim 10, wherein said feeding meansincludes a measuring device for admitting to said conveyor tobacco at aconstant rate.

17. Apparatus as defined in claim 16, wherein said measuring devicecomprises means for weighing unit lengths of said tobacco stream, anadjustable second conveyor for supplying tobacco to said weighing means,and means for adjusting said second conveyor in response to deviationsof the measured quantity of tobacco from a predetermined quantity.

18. Apparatus as defined in claim 10, further comprising means forcooling the tobacco which issues from said conditioning zone.

19. Apparatus for conditioning tobacco, comprising a conveyor definingan elongated conditioning zone;

feeding means for delivering to said conveyor a stream of moist tobaccowhereby said stream advances in a predetermined direction through andbeyond said conditioning zone; first adjustable heating means forheating said conveyor to thereby subject tobacco in said conditioningzone to a first heating and moistureexpelling action; second adjustableheating means for conveying through said conditioning zone a hot fluidcounter to said direction to thus subject tobacco in said zone to asecond heating and moisture-expelling action; measuring means fordetermining the moisture content of tobacco after the tobacco issuesfrom said conditioning zone; and regulating means connected with saidmeasuring means and operative to adjust said first and second heatingmeans in response to deviations of that moisture content which isdetected by said measuring means from a predetermined value, saidregulating means comprising discrete first and second regulating unitsfor said first and second heating menas and said second unit comprisingdetector means arranged to produce signals indicating the temperature ofsaid fluid, said second regulating unit further comprising adjustingmeans for changing the temperature of said fluid in response to saiddeviations; and means including a differential circuit for transmittingto said first regulating unit signals from said detector means foradjustment of said first heating means in dependency on changes intemperature of said fluid as a function of time.

20. Apparatus as defined in claim 19, further comprising means forcontrolling the transmission of signals from said circuit to said firstregulating means so that the latter receives signals only when suchsignals indicate sudden changes in the temperature of said fluid.

1. A method of conditioning tobacco, comprising the steps of conveying astream of moist tobacco on a conveyor in a predetermined directionthrough an elongated conditioning zone; subjecting tobacco in saidconditioning zone to indirect heating action by heating the conveyor;subjecting tobacco in said conditioning zone to the direct heatingaction of a fluid by conveying said fluid through said conditioning zonecounter to said direction with attendant reduction of the moisturecontent of tobacco as a consequence of said direct and indirect heatingactions; measuring the moisture content of tobacco downstream of saidconditioning zone; comparing the result of such measurement with apredetermined value; automatically adjusting said direct and indirectheating actions in response to deviations of said result from saidpredetermined value; and adjusting one of said heating actions independency upon the other of said heating actions.
 2. A method asdefined in claim 1, wherein said indirect heating action issubstantially uniform throughout said conditioning zone.
 3. A method asdefined in claim 1, wherein said first mentioned adjusting stepcomprises changing the temperature of said fluid.
 4. A method ofconditioning tobacco, comprising the steps of conveying a stream ofmoist tobacco on a conveyor in a predetermined direction through anelongated conditioning zone; subjecting tobacco in said conditioningzone to the indirect heating action of a first fluid by utilizing thefirst fluid to heat the conveyor; subjecting tobacco in saidconditioning zone to the direct heating action of a second fluid byconveying the second fluid through said conditioning zone counter tosaid direction with attendant reduction of the moisture content oftobacco as a consequence of said direct and indirect heating actions;measuring the moisture content of tobacco downstream of saidconditioning zone; comparing the result of such measurement with apredetermined value; and automatically adjusting said direct andindirect heating actions in response to deviations of said result fromsaid predetermined value, said adjusting step comprising changing thetemperature of said second fluid, measuring the temperature of saidsecond fluid, and changing said indirect heating action in response tochanges in the temperature of said second fluid.
 5. A method ofconditioning tobacco, comprising the steps of conveying a stream ofmoist tobacco on a conveyor in a predetermined direction through anelongated conditioning zone; subjecting tobacco in said conditioningzone to the indirect heating action of a first fluid by utilizing thefirst fluid to heat the conveyor; subjecting tobacco in saidconditioning zone to the direct heating action of a second fluid byconveying the second fluid through said conditioning zone counter tosaid direction with attendant reduction of the moisture content oftobacco as a consequence of said direct and indireCt heating actions;measuring the moisture content of tobacco downstream of saidconditioning zone; comparing the result of such measurement with apredetermined value; automatically adjusting said direct and indirectheating actions in response to deviations of said result from saidpredetermined value, including changing the temperature of said secondfluid; measuring the intensity of said indirect heating action;producing first and second signals respectively indicating thetemperature of said second fluid and the intensity of said indirectheating action; and changing the intensity of said indirect heatingaction in accordance with said signals.
 6. A method as defined in claim5, wherein said adjusting step further comprises changing thetemperature of said second fluid in accordance with said second signal.7. A method as defined in claim 4, wherein said indirect heating actionis changed in dependency on changes in temperature of said second fluidas a function of time.
 8. A method as defined in claim 1, furthercomprising the step of cooling the tobacco which issues from saidconditioning zone prior to said measuring step.
 9. A method as definedin claim 1, further comprising the step of supplying to saidconditioning zone moist tobacco at an at least substantially constantrate.
 10. Apparatus for conditioning tobacco, comprising a conveyordefining an elongated conditioning zone; feeding means for delivering tosaid conveyor a stream of moist tobacco whereby such stream advances ina predetermined direction through and beyond said conditioning zone;first adjustable heating means for heating said conveyor to therebysubject tobacco in said zone to a first heating and moisture-expellingaction; second adjustable heating means for conveying through saidconditioning zone a hot fluid counter to said direction to thus subjecttobacco in said zone to a second heating and moisture-expelling action;measuring means for determining the moisture content of tobacco afterthe tobacco issues from said conditioning zone; and regulating meansconnected with said measuring means and operative to adjust said firstand second heating means in response to deviations of that moisturecontent which is detected by said measuring means from a predeterminedvalue and for adjusting the heating action of one of said heating meansin dependency upon the heating action of the other of said heatingmeans.
 11. Apparatus as defined in claim 10, wherein said conveyorcomprises a tubular member which surrounds said conditioning zone andsaid first heating means is arranged to heat said tubular member, saidtubular member having an intake end for admission of tobacco and adischarge end for evacuation of tobacco and for admission of said hotfluid.
 12. Apparatus as defined in claim 10, wherein said regulatingmeans comprises discrete first and second regulating units for saidfirst and second heating means and said second regulating unit comprisesadjusting means for changing the temperature of said fluid as a functionof said deviations.
 13. Apparatus for conditioning tobacco, comprising aconveyor defining an elongated conditioning zone; feeding means fordelivering to said conveyor a stream of moist tobacco whereby saidstream advances in a predetermined direction through and beyond saidconditioning zone; first adjustable heating means for heating saidconveyor to thereby subject tobacco in said zone to a first heating andmoisture-expelling action; second adjustable heating means for conveyingthrough said conditioning zone a hot fluid counter to said direction tothus subject tobacco in said zone to a second heating andmoisture-expelling action; measuring means for determining the moisturecontent of tobacco after the tobacco issues from said conditioning zone;and regulating means connected with said measuring means and operativeto adjust said first and second heating means in response to deviationsof that moisture content which is detected by said meAsuring means froma predetermined value, said regulating means comprising discrete firstand second regulating units for said first and second heating means,said measuring means being connected with said second regulating unit toeffect changes in the temperature of said fluid in response to saiddeviations and said second regulating unit comprising detector means forproducing signals indicating the temperature of said fluid, said firstregulating unit being responsive to said signals to adjust said firstheating means as a function of changes in the temperature of said fluid.14. Apparatus for conditioning tobacco, comprising a conveyor defining aelongated conditioning zone; feeding means for delivering to saidconveyor a stream of moist tobacco whereby said stream advances in apredetermined direction through and beyond said conditioning zone; firstadjustable heating means for heating said conveyor to thereby subjecttobacco in said conditioning zone to a first heating andmoisture-expelling action; second adjustable heating means for conveyingthrough said conditioning zone a hot fluid counter to said direction tothus subject tobacco in said conditioning zone to a second heating andmoisture-expelling action; measuring means for determining the moisturecontent of tobacco after the tobacco issues from said conditioning zone;and regulating means connected with said measuring means and operativeto adjust said first and second heating means in response to deviationsof that moisture content which is detected by said measuring means froma predetermined value, said regulating means comprising discrete firstand second regulating units for said first and second heating means andsaid first and second regulating units respectively comprising first andsecond detector means for producing first and second signalsrespectively indicating the temperature of said conveyor and thetemperature of said fluid, said first regulating unit further comprisingadjusting means for adjusting said first heating means to thereby changethe temperature of said conveyor in response to said signals, saidsecond regulating unit including adjusting means for changing thetemperature of said fluid in response to said deviations.
 15. Apparatusfor conditioning tobacco, comprising a conveyor defining an elongatedconditioning zone; feeding means for delivering to said conveyor astream of moist tobacco whereby said stream advances in a predetermineddirection through and beyond said conditioning zone; first adjustableheating means for heating said conveyor to thereby subject tobacco insaid conditioning zone to a first heating and moisture-expelling action;second adjustable heating means for conveying through said conditioningzone a hot fluid counter to said direction to thus subject tobacco insaid conditioning zone to a second heating and moisture-expellingaction; measuring means for determining the moisture content of tobaccoafter the tobacco issues from said conditioning zone; and regulatingmeans connected with said measuring means and operative to adjust saidfirst and second heating means in response to deviations of thatmoisture content which is detected by said measuring means from apredetermined value, said regulating means comprising discrete first andsecond regulating units for said first and second heating means and saidfirst and second regulating units respectively comprising first andsecond detectors for producing signals respectively indicating thetemperature of said conveyor and the temperature of said fluid, saidsecond regulating unit further comprising adjusting means for changingthe temperature of said fluid as a function of signals from said firstdetector and in response to said deviations.
 16. Apparatus as defined inclaim 10, wherein said feeding means includes a measuring device foradmitting to said conveyor tobacco at a constant rate.
 17. Apparatus asdefined in claim 16, wherein said measuring device comprises means forweighing unit lengths oF said tobacco stream, an adjustable secondconveyor for supplying tobacco to said weighing means, and means foradjusting said second conveyor in response to deviations of the measuredquantity of tobacco from a predetermined quantity.
 18. Apparatus asdefined in claim 10, further comprising means for cooling the tobaccowhich issues from said conditioning zone.
 19. Apparatus for conditioningtobacco, comprising a conveyor defining an elongated conditioning zone;feeding means for delivering to said conveyor a stream of moist tobaccowhereby said stream advances in a predetermined direction through andbeyond said conditioning zone; first adjustable heating means forheating said conveyor to thereby subject tobacco in said conditioningzone to a first heating and moisture-expelling action; second adjustableheating means for conveying through said conditioning zone a hot fluidcounter to said direction to thus subject tobacco in said zone to asecond heating and moisture-expelling action; measuring means fordetermining the moisture content of tobacco after the tobacco issuesfrom said conditioning zone; and regulating means connected with saidmeasuring means and operative to adjust said first and second heatingmeans in response to deviations of that moisture content which isdetected by said measuring means from a predetermined value, saidregulating means comprising discrete first and second regulating unitsfor said first and second heating menas and said second unit comprisingdetector means arranged to produce signals indicating the temperature ofsaid fluid, said second regulating unit further comprising adjustingmeans for changing the temperature of said fluid in response to saiddeviations; and means including a differential circuit for transmittingto said first regulating unit signals from said detector means foradjustment of said first heating means in dependency on changes intemperature of said fluid as a function of time.
 20. Apparatus asdefined in claim 19, further comprising means for controlling thetransmission of signals from said circuit to said first regulating meansso that the latter receives signals only when such signals indicatesudden changes in the temperature of said fluid.